Typical web rewinding machines provide a number of core supporting mandrels ranging anywhere from four to ten in number which are mounted on an indexingly rotatable turret. The mandrels extend parallel to the horizontal axis about which the turret rotates, and they are spaced at equal distances from the turret axis and at uniform intervals around that axis. By way of example, a typical six-mandrel turret moves through one-sixth of a revolution at each of its indexing movements and hence it carries each mandrel in turn to each of the six successive stations with a period of dwell at each station. By way of yet another example, an exemplary eight-mandrel turret moves through one-eighth of a revolution at each of its indexing movements and hence it carries each mandrel in turn to each of the eight successive stations with a period of dwell at each station. In an alternative embodiment, a ten-mandrel turret can rotate at a constant angular velocity and the mandrels travel through a non-circular closed path. In any regard, it should be understood that the number of spindles disposed about any given turret used in a web rewinding machine would likely determine the number of successive stations in any such device.
In such a configuration, typically one station (sometimes called a first station) is a loading station at which a length of core stock is slid axially onto the mandrel. At the next station, the core stock has an adhesive or glue applied to the surface of the core. At the third station, the mandrel is brought up to winding speed. As the mandrel moves from the third to the fourth station, the web material is attached to the glued core disposed upon the mandrel for the beginning of the winding operation. Winding continues while the mandrel is at the fourth station. As the mandrel moves out of the fourth station, and after the desired length of web has been wound, the web material is cut through across its width (or cross-machine direction) to sever it from the wound roll of web material (e.g., the source of the web material) and give it a new leading edge that is attached to a new core on the next mandrel moving into the winding station. At the fifth station, the rotation of the mandrel is decelerated to a stop, and at the sixth station a wound core or log is stripped off the mandrel. The mandrel then moves to the first station for a repetition of the cycle.
A conventional turret by which the mandrels are carried comprises a spider which is mounted for a rotation on a coaxial shaft that projects a substantial distance in one direction from the spider. The mandrels have rotating connections with the spider, and they project from it in the same direction as the turret shaft. The rotating connection of each mandrel with the spider must provide cantilevered support of the mandrel because when the mandrel is at the core loading station and the unloading station, the end of the mandrel that is remote from the spider is disengaged from supporting parts and completely accessible to allow cores to be moved axially onto and off. It should be recognized that the mandrels tend to be heavy and very long—typically, 72 inches to 96 inches in length. Therefore, their free ends are typically supported whenever possible and certainly during winding.
To provide support of the free ends of the mandrels, there is conventionally an assembly of supporting arms or chucks on the end portion of the turret shaft that is remote from the spider. This is also known to those in the art as a mandrel cupping assembly. A mandrel cupping assembly is an assembly that is constrained to indexing rotation concurrent with the spider containing the individual mandrels. The mandrel cupping spider generally comprises a chuck arm (or cup) cooperatively associated with each mandrel. Each chuck arm is generally swingable about an axis which is near the turret axis and transverse thereto between a substantially radially extending closed position in which the free end of the chuck arm supportingly engages the free end portion of its associated mandrel and an open position in which the chuck arm is disengaged from its mandrel and is disposed in a more or less axial orientation alongside the turret shaft. Each chuck arm is operated automatically so that it is in its open position during loading and unloading of the mandrel and is in its closed position at least from the time the mandrel moves into the gluing station and moves out of the deceleration station mentioned supra.
In one embodiment, a conventional mechanism for actuating the mandrel supporting chuck arms is provided with a barrel cam that is fixed to the machine frame adjacent to the free ends of the mandrels and a lever and link arrangement for each chuck arm. Each arrangement is carried by the turret for rotation therewith and having a cam follower roller that rides in a groove in the periphery of the stationary barrel cam. Each chuck arm is actuated at appropriate times in consequence of indexing movement of the turret. The shape of the cam groove is provided so that the chuck arms move into engagement with their respective mandrels when the latter are generally adjacent the glue applicator wheels and retract when the mandrels move from the web material winding position.
In such an operation, the stripping of wound rolls off a mandrel is conventionally accomplished by means of a pusher that engages the log at only one side of the mandrel and provides a lateral force upon the cantilevered mandrel. This can set the mandrel into a vibration mode that may be aggravated by the indexing movement that follows unloading. With the mandrel unsupported at the loading station, its free end often wobbles so severely that the core may not be run onto it with automatic core loading equipment. Such an apparatus is described in U.S. Pat. No. 2,769,600.
It is believed that with such conventional machines, the failure to load a core creates a danger that the mandrel itself would be coated with glue at the gluing station necessitating a lengthy shutdown of the machine for cleaning. An operator, seeing that such an unloaded mandrel was moving out of the unloading station, would be required to stop the machine and would find that there is no way to retract the chuck arm engaged with the empty mandrel to permit manual axial unloading of the core. This is because of the nature of the chuck arm actuating mechanism. One purported solution to this problem was to slit a core along its length and push it laterally onto a mandrel to protect the mandrel from glue. At the conclusion of the winding cycle the individual rolls wound onto the slitted core are then discarded.
It is also believed that wobble of an unsupported mandrel could cause a chuck arm to fail to engage the mandrel properly. One solution proposed was a U-shaped member on each chuck arm that tended to preliminarily engage the mandrel during closing movement of the chuck arm and steady the mandrel sufficiently to enable its conical free end to be received in the bearing socket disposed in the chuck arm. However, it is believed that this expedient is not always successful in practice because as the wobbling mandrel fails to enter the chuck arm socket, the chuck arm mechanism exerts as much force as the indexing mechanism can provide. This can result in the inevitable bending or breakage of the link and lever elements that translate any cam follower motion into swinging motion of the chuck arm. The repair of such damage would be necessarily difficult and time consuming.
It is also believed that another expedient that has been used to prevent damage to the chuck arm actuating mechanism is to mount the barrel cam for limited axial motion and pneumatically bias it towards one limit of such motion. When a chuck arm fails to close properly, the reaction force that is imposed upon the cam moves it against its bias to a position which actuates an emergency stop. However, it is believed that such an emergency shutdown arrangement merely relieves some of the effects of the problem rather than solving the problem itself. By way of example, it will not permit axial loading of a core onto an empty mandrel that had moved out of the loading position.
Other solutions provide an automatic web rewinding machine or an automatic mandrel chucking mechanism that does not employ force derived from the turret indexing to affect chuck arm actuation. The chuck arms move to and from their mandrel supporting positions only during periods of dwell to minimize the likelihood of mandrel vibration at the time chuck arm closing occurs. The mechanism is arranged to allow a chuck arm to be manually controlled for movement to its open position in any position of the turret so that a core can be axially loaded onto an empty mandrel or a defective core or roll can be axially stripped off the mandrel. Such a system is described in U.S. Pat. No. 4,266,735.
In any regard, attempts by the prior art to achieve an automatic web rewinding machines all provide for a single chuck arm and its associated equipment to be cooperatively associated with a respective mandrel. Further, the chuck arm and its associated equipment must cooperatively rotate with the mandrel about the turret axis. In other words, a chuck arm is constrained to rotate with the turret and is movable relative to and between a closed position (in which the chuck arm supportingly engages the other end of the mandrel) and an open position (in which the chuck arm is disengaged from the mandrel) to permit cores to be moved axially onto and off it. Clearly, the mechanism is unduly complex and requires numerous moving parts and associated ancillary equipment for it to perform its intended function.
Thus, it would be clearly advantageous to provide a turret system and in particular, a mandrel cupping assembly that is less complex and requires fewer moving parts to perform its intended function. In fact, such a system would rotate only the mandrel cup with its respective mandrel free of any associated equipment necessary to load and unload the mandrel cup. Clearly, such systems would be appreciated by one of skill in the art because of their overall simplicity and ease of use.